Thermoplastic compositions

ABSTRACT

GRAFT COPOLYMERS COMPRISING A SUBSTRATE OF A DIENE RUBBER AND A SUPERSTRATE CONTAINING A HIGH PROPORTION OF COPOLYMERISED ACRYLONITRILE AND BLENDS OF SUCH GRAFT COPOLYMERS WITH POLYMERS CONTAINING A HIGH PROPORTION OF ACRYLONITRILE UNITS.

United States Patent 3,816,563 THERMOPLASTIC COMPOSITIONS Carl FraserMathews, 4 Bramshot Close, London Road,

Hitchin, England; Eric Nield, 12A Beane Road, Watton-at-Stone, England;John Brewster Rose, Uluvia, Pasture Road, Letchworth, England; and PeterIncledon Vincent, 27 Coneydale, Welwyn Garden City, England No Drawing.Continuation-impart of application Ser. No. 860,100, Sept. 22, 1969,which is a continuation of application Ser. No. 539,738, Apr. 4, 1966,both now abandoned. This application Mar. 22, 1972, Ser. No.

Int. or. cost 19/18 US. Cl. 260-876 R 6 Claims ABSTRACT OF THEDISCLOSURE Graft copolymers comprising a substrate of a diene rubber anda superstrate containing a high proportion of copolymerisedacrylonitrile and blends of such graft copolymers with polymerscontaining a high proportion of acrylonitrile units.

This application is a continuation-in-part application of ourapplication Ser. No. 860,100 filed Sept. 22, 1969, now abandoned, whichwas a continuation application of our application Ser. No. 539,738 filedApr. 4, 1966, now abandoned.

This invention relates to thermoplastic compositions derived from adiene rubber and a resin, and to the production of shaped articlestherefrom.

In particular, it relates to graft copolymers comprising a substrate ofa diene rubber and a superstrate containing a high proportion ofcopolymerised acrylonitrile, and to blends of such graft copolymers withpolymers containing a high proportion of acrylonitrile units. Theproducts of the invention are tough and at the same time rigid andunusually hard.

The superstrate contains a high proportion of acrylonitrile with atleast one other ethylenically unsaturated monomer copolymerisable usingfree-radical catalysts, not being a conjugated aromatic olefine. Inparticular, one of the comonomers may be an g-aryl maleimide providingat least 1% molar of the units in the superstrate. Aromaticallyconjugated monomers such as styrene and u-methylstyrene are excludedfrom the superstrate owing to their normally inhomogeneouscopolymerisation with acrylonitrile. Rubber-free resins from thesuperstrate monomers are exceptionally strong materials with highsoftening points, but they are insufiiciently tough for many purposes.

The superstrate contains from 45% to 90% (preferably 60% to 84%) molarof units from acrylonitrile, from 0% to 20% (preferably not more than10%) molar of units from at least one II -aryl maleimide, and from to35% (preferably 15% to 30%) molar of units from at least one otherethylenically unsaturated monomer copolymerisable using free radicalcatalysts but not including a conjugated aromatic olefine.

The g-aryl maleimides are conveniently obtained from anilines (primaryarylamines). Many different anilines are readily available and yieldE-aryl maleimides that may be used as comonomers for the copolymers. Thearyl substituent is derived from an aromatic hydrocarbon or heterocyclein which one or more of the hydrogen atoms may be replaced by otheratoms or groups.

'Substituents containing active hydrogen atoms, however,

are generally to be avoided because they may interfere withpolymerisations catalysed by free radicals. The aryl groups that may bepresent in the E-aryl maleimides include, for example phenyl,4-diphenyl, l-naphthyl, all the 3,816,563 Patented June 11., 1974monoand di-methylphenyl isomers, 2,6-diethylphenyl, 2-, 3- and4-chlorophenyl, 4-bromophenyl and other monoand di-halophenyl isomers,2,4,6-trichlorophenyl, 2, 4,6-tribromophenyl, 4-n-butylphenyl,2-methyl-4-n-butylphenyl, 4-benzylphenyl, 2-, 3- and 4-methoxyphenyl,2-, 3- and 4-ethoxyphenyl, 2,5-diethoxyphenyl, 4-phenoxyphenyl,4-methoxycarbonylphenyl, 4-cyanophenyl, 2-, 3- and 4-nitrophenyl andmethylchlorophenyl (2,3-, 2,4-, 2, 5- and 4,3-isomers). TheE-(o-substituted phenyl) maleimides are generally less coloured than theother isomers or the unsubstituted compounds and may therefore bepreferred if a relatively colourless product is desired.

The other ethylenically unsaturated monomer is any such monomer (otherthan a conjugated aromatic olefine) that is copolymerisable usingfree-radical catalysts. Such monomers usually (but not always) containolefinic methylene groups, and include for example, alkenes such asethylene, propylene, butene-l, isobutene, pentene- 1, hexene-1,2-methylbutene-1, Z-methylphentene-l, 4- methylpentene-l,2,4,4-trimethylpentene-1, octene, octadecene, cyclohexene andmethylenecyclohexane, dienes such as butadiene and norbornadiene, estersof acrylic and methacrylic acids such as methyl, ethyl, n-butyl and2-ethylhexyl acrylates and methyl and n-butyl methacrylates, vinylesters such as vinyl acetate, vinyl ethers such as methyl and ethylvinyl ethers, esters of fumaric acid, and unsaturated nitriles such asmethacrylonitrile, vinylidene cyanide, a-methyleneglutaronitrile,a-acetoxyacrylonitrile, u-cyanostyrene, and esters of a-cyanoacrylicacid. In minor amounts, there may be present for example vinyl chloride,vinylidene chloride, u-chloroacrylonitrile, diallyl ether, divinyl etherand glycol dimethacrylate.

The diene rubber in the substrate contains from 40% to molar of at leastone conjugated 1,3-diene monomer and from 0% to 60% of at least oneother ethylenically unsaturated monomer copolymerisable withfree-radical catalysts. Suitable dienes include for example, butadiene,isoprene, 2,3-dimethylbutadiene, piperylene and chloroprene. Ascomonomers acrylonitrile and styrene are particularly convenient,although a wide variety of other monomers may be used, including many ofthose listed above as examples of ethylenically unsaturated comonomersfor the superstrate. Diene homopolymers (e.g. polybutadiene) andcopolymers with a low proportion of comonomer have lower glasstransition temperatures and may therefore be preferable especially whenthe product is required for service at low temperatures.

The compositions of the invention can be produced by a processcomprising sequential polymerisation. In this process, the monomers forthe superstrate are polymerised by free-radical catalysis in thepresence of the diene rubber. The process is carried out using theappropriate techniques for polymerisation catalysed by free radicals,conveniently in bulk or in aqueous suspension or emulsion. A similaremulsion process or a stereospecific process may be used to make thediene rubber. The graft copolymer may then be employed as a latex orisolated from the polymerisation medium, freed from residual monomers,and dried. The product of this sequential polymerisation may be blendedif desired with a resin, e.g. a resin formed from the superstratemonomers. This blending step can be used to produce tough and strongcompositions. The graft are therefore, according to the invention,useful materials for blending with resins to give tough compositions.The resin used for blending is not necessarily one made from the samemonomers as the grafted portion but can be any resin of ade-. quatestrength especially one having a high content of nitrile groups. Thismay be for example a copolymer of 3 acrylonitrile (45% to 90% molar,preferably 60% to 84% molar) with at least one other copolymerisableethylenically unsaturated monomer, e.g. a homogeneous copolymer with aconjugated aromatic olefine. The resin may also contain to 20% of atleast one l I -aryl maleimide, particularly 1 to 20% although 0 to 1%may be present.

A product in many ways equivalent to such a blend may also be obtaineddirectly by adjusting the conditions of the grafting polymerisation sothat some of the superstrate monomers copolymerise to give some separateresin as well as the graft.

The resultant products are thus composed at least partially of the typeof material usually referred to as graft copolymer. It is possible,however, that the superstrate in the grafted material is not allchemically bonded to the rubber but contains resin from the superstratemonomers associated with the rubber in a much more intimate physicalmixture than can normally be obtained by blending preformed polymers.

The amount of rubber in the final blend is not the only factor governingtoughness, which depends also on the amount of resin grafted on to therubber in the graft used for blending.

Preferably, the blend comprises from 1% to 50% by weight of the dienerubber. Compositions containing below 25% of the rubber are particularlyhard scratchresistant materials with high impact strength, and whilethere is an apparently smooth transition of properties the compositionscontaining at least 20% (preferably not more than 40%) of the rubbertend to be hard materials with very high impact strength. In the blendthe weight ratio of superstrate to resin should be less than 1.6. Theratio is given by the formula bc/ 100 (a-c) where a is weight percentageof rubber in the graft, b is the weight percentage of superstrate in thegraft and c is the weight percentage of rubber in the blend.

Preferred blends according to the invention, unlike some rubber/ resinblends, show no apparent separation of phase on warming from 180 C. to+20 C.

The compositions of the invention, mixed with any desired fillers orreinforcing materials, lubricants and stabilisers, can be used asthermoplastic raw materials to make articles which require a goodresistance to impact. Their toughness coupled with high strength andhigh softening point may thus be displayed to advantage. For example,the compositions may be extruded into sheet or tube, and the sheet canbe calendered with embossing if desired or can be shaped as required,e.g. by pressing, drawing or vacuum-forming. The compositions can alsobe compression-moulded and injection-moulded. Examples of articles thatmay thus be produced using the compositions of the invention includepanelling and exterior casing for machinery (as in motor cars, officemachines and household equipment), crash helmets, pipes for conveyingfluids, and telephone receivers. The use of compositions of theinvention having superior tensile strength coupled with rigidity andtoughness may allow enconomy of material in comparison with currentlyused products in that thinner pieces would serve the same purpose. Theadvantageous physical properties of the compositions may also permitthem to be used in enginering applications for which plastics have nothitherto been suitable.

The toughness of a material such as a thermoplastic polymer is connectedwith the amount of energy that the material is capable of absorbingwithout breaking when stressed in tension, and this in turn is relatedto the way in which the material behaves when stressed in tension atdifferent temperatures. When an increasing uniaxial tensile stress isapplied at any one temperature, the material will eventually eitherbreak or yield. The material breaks before yielding if it is brittle,and whether or not it is brittle depends on the temperature. There is atemperature (the brittle point) peculiar to any particular materialabove which it undergoes brittle fracture. At temperatures below thebrittle point, the amount of energy the material can absorb whenstressed in tension is low and varies little with temperature. Above thebrittle point, however, the amount of energy that can be absorbed risessteeply as the temperature increases. To be tough at room temperature,therefore, a material should have a relatively low brittle point.

The brittle points of two different materials can be compared indirectlyby comparing their properties under stress, first at a low temperaturewhere both materials are brittle, and secondly at a higher temperaturewhere neither material is brittle. Convenient temperatures for thesetests are obtained by using liquid nitrogen (the sample being at about180 C.) and room temperature (+20 C.) respectively. Up to its brittlepoint, the stress at which a material breaks falls only slightly as thetemperature increases. Above the brittle point, however, the stress atwhich the material yields falls relatively steeply as the rise oftemperature continues. Consider therefore two materials which break atthe same stress at l C. but have different brittle points. The materialwith the lower brittle point (the tougher material) will yield at thelower stress at +20 C. Conversely, the tougher of two differentmaterials yielding at the same stress at +20 C. will be the one whichbreaks at the higher stress at C.

In order to toughen a material, therefore, it is desirable to alter itscomposition so as to preserve a high resistance to brittle fracture at--l80 C. but reduce the stress at which it yields at +20 C.

Resins containing a high proportion of homogeneously copolymerisedacrylonitrile have unusually high breaking stresses at 180 C. and highyielding stresses at +20 C. According to the invention it has been foundthat graf copolymers and their blends may be produced so as largely toretain the high breaking stress at l80 C. but having a reduced yieldingstress at +20 C. Owing to the high breaking stress at l80 C., theyielding stress at +20 C. can be reduced sufficiently for the product tobecome tough while remaining adequately rigid and hard. The inventionaccordingly provides materials which have a good resistance to impactcoupled with excellent structural properties.

The breaking stress at 180 C. was measured on specimens 51 mm. long and12.7 mm. wide milled from a compression-moulded sheet 3 mm. thick. Thespecimen rested on two supports 38.1 mm. apart and midway between them aload was applied sufficient to bend the specimen at the rate of 457mm./min. The breaking stress was calculated by multiplying the load atthe moment of rupture by the factor:

The yielding stress at +20 C. was measured on specimens 76 mm. long and14 mm. wide milled from a compression-moulded sheet 3 mm. thick. Thecross-sectional area across the centre of the specimen was reduced to 9mm. by milling two slots (radius of curvature 31 mm.) opposite eachother in the long edges so that the narrowest width of the specimen was3 mm. A tensile stress was then applied to the specimen sufiicient toelongate it at the rate of 12.7 mm./min. and the stress at the yieldpoint was recorded.

For comparison with the data of the examples below, the fiexuralbreaking stress at 180 C. of the rubber-free resins formed from thesuperstrate monomers is usually about 25 kg./mm. and the tensileyielding stress is usually about 11 kg./mm. The compositions of theinvention often largely retain the high breaking stress at 180 C.characteristic of the resins but have improved toughness (as may beindicated by the greatly reduced yielding stress).

As explained above, a useful indication of the relative toughness ofmaterials is often given by comparing their flexural breaking stressesat -180 C. and their tensile yielding stresses at +'20 C. With materialsthat are so tough as not to be brittle in the tensile test at -40 C.,however, this approach loses some of its value. An addi tional test (thenotched specimen impact test) has therefore been used to supplement thecomparative measurements on such materials.

In this test, a specimen 60 mm. long, 6.5 mm. Wide and 3 mm. thick wasgiven a 45 notch 2.8 mm. deep (tip radius not more than 0.25 mm.) in thecentre of one edge. It was supported between two supports 50 mm. apartand struck centrally on the edge opposite the notch by a pendulumdropping from 30 cm. with more than su'fiicient energy to break thespecimen. From the residual energy of the pendulum the energy requiredto break the specimen was calculated and divided-by the cross-sectionalarea of the specimen at the notch. The resulting value (expressed injoules/cm?) represented the energy required to cause cracks to propagatein the material.

Using this test at room temperature (20-26 C.), various ABS materialsbroke at 0.5 J/cm. or somewhat above. Compositions of the invention havebeen found to have similar toughness in this test; for example theprducts of Example 1 and Example 7 broke at 0.47 J/cm. and 0.44 J/cm?respectively. Thus compositions of the invention possess toughness incombination with exceptionally high tensile strength.

The following examples illustrate the invention. Breaking stress,yielding stress, and toughness were measured as described above.Measurements were made at +20 C. (room temperature) unless otherwiseindicated.

EXAMPLE 1 Acrylonitrile (75% molar), N -phenylmaleimide (5% molar) andisobutene (20% molar) monomers were copolymerised in the presence of arubber latex, notshortstopped, formed of 30% molar acrylonitrile and 70%molar butadiene and containing 49.4% solids of which 77% was insolublein methyl ethyl ketone.

' The latex (55.85 g.) was brought to pH 5.7 with 0.1 E sulphuric acidand placed in a shaking autoclave. A solution of 1 I -phenylmaleimide(14.25 g.) in acrylonitrile (65.8 g.) was added, together with water(650 cm. potassium persulphate (1.55 g.) and sodium rnetabisulphite(1.03 g.). The contents of the autoclave were repeatedly pressurised to7 kg./cm. with nitrogen and vented. Isobutene 18.8 g.) was then addedand the reaction mixture was maintained at 30 C. for 18 hours undernitrogen at 7 -kg./cm. The solid composition (97.1 g.) was isolated byadding an aqueous solution (10 cm. of calcium chloride saturated at roomtemperature, washing the solid six times with water at 90 C. and thenwith cold methanol, and drying under vacuum at 70 C. Assuming that theproduct comprised all the rubber initially employed, it contained 28.4%rubber and 20% butadiene. The full Vicat and one-tenth Vicat softeningpoints of the material were 102 C. and 93 C. respectively.

On compression-moulding the composition gave a clear yellow plaque. Itsbreaking stress at -180 C. and yielding stress at +20 C. wererespectively 25 kg./mm. and 5.9 kg./mm. Similar measurements oncommercially available acrylonitrile/ butadiene/ styrene terpolymers andblends (ABS materials) showed breaking stresses at -180 C. of 13 to 17kg./mm. and yielding stresses at +20 C. of 3.9 to 5.6 kg./mm.

The melt viscosity of the composition was 12.5 kp. at 260 C., measuredat a shear rate of 100/ s. The extrudate was transparent and pale yellowand the melt viscosity remained unchanged over five minutes at 260 C.

EXAMPLE 2 The process described in Example 1 was repeated, using arubber latex (67.9 g.) formed of 21% molar acrylonitrile and 79% molarbutadiene and containing'40.7%

solids.

The isolated solid composition (105 g.) contained 26.3 rubber and 18%butadiene. The full Vicat and onetenth Vicat softening points were C.and 91 C. respectively. Its breaking stress at C. was 22 kg./ mm. andits yielding stress at +20 C., 0 C., -20 C. and -40 C. was 5.7, 7.4, 9.0and 104 kg/mm. respectively. At 60 C. it was brittle, breaking at 12.7kg./ mm. Its melt viscosity was 17 kp. at 260 C., measured at 1000/s.

EXAMPLE 3 The process described in Example 1 was repeated, using 74.96g. of the rubber latex at its unadjusted pH of 7.3.

The isolated solid composition (111 g.) contained 33.3% rubber and 23.8%butadiene. The full Vicat and one-tenth Vicat softening point were 102C. and 91 C. respectively. Its breaking stress at l80 C. was 23 kg./ mm.and its yielding stress at +20 C., 0 C., 20 C., -40 C. and --60 C. was5.1, 6.5, 8.2, 10.1 and 13.3 kg./mm. respectively. Its melt viscositywas 14 kp. at 260 C., measured at 1000/s.

EXAMPLE 4 The process described in Example 1 was repeated, using arubber latex (38.95 g.) formed of 21% molar acrylonitrile and 79% molarbutadiene and containing 47.5% solids.

The isolated solid composition (98 g.) contained 18% rubber and 14.5%butadiene. The full Vicat and onetenth Vicat softening points were 108C. and 71 C. respectively. Its yielding stress at +80" C., +60 C., +20C.- and 20 C. was 2.4, 3.8, 6.3 and 9.3 kg./mm. respectively. At 60 C.it was brittle, breaking at 14.4 kg./mm.

EXAMPLE 5 The process described in Example 1 was repeated, using arubber latex (77.9 g.) of the same molar composition but containing47.5% solids.

The isolated solid composition (112 g.) contained 33% rubber and 26%butadiene. The full Vicat and one-tenth Vicat softening points were 103C. and 93 C. respectively. Its yielding stress at -+80 C., +60 C., +20C., 20 C. and +60 C. was 1.5, 3.0, 5.0, 7.5 and 12.6 kg./ mm.respectively.

EXAMPLE 6 The process described in Example 1 was repeated, using arubber latex (87.8 g.) of the same molar composition but containing 47.5solids.

The isolated solid composition (96.8 g.) contained 42.9% rubber. and33.8% butadiene. The full Vicat and one-tenth Vieatsgftening points were103 C. and 91 C. respectively. Its. yielding stress at +80 C., +60 C.,

+20 C., -20 C. and 60 C. was 1.2, 2.1, 3.6, 5.7 and 10.8 kg./mm.respectively.

EXAMPLE 7 Acrylonitrile (75 molar), E-Z-chlorophenylmaleimide (5% molar)and methyl acrylate (20% molar) monomers were copolymerised in thepresence of a rubber latex, not short-stopped, formed of 32% molaracrylonitrile and 68% molar butadiene and containing 48.4% solids, asdescribed in Example 1.

The latex (57.06 g.; 27.6 g. solids) was brought to pH 5.7.Acrylonitrile (65.8 g.) and methyl acrylate (28.55 g.) were added,together with sodium rnetabisulphite (0.33 g.), potassium persulphate(0.5 g.) and water (650 cm. The polymerisation was conducted asdescribed in Example 1 for 21 hours at 30 C. to yield 112 g. solids. Theisolated composition contained 24.7% rubber and 16.9% butadiene. Oncompression-moulding at 200 C. it gave a transparent pale yellow plaque.This had a breaking stress at -180 C. of 23.2 kg./mm. a yielding stressat +20 C. of 7.2 kg./mm. and a melt viscosity of 20 kp. at 260 C. and ashear rate of 1000/s.

7 EXAMPLE 8 The process described in Example 7 was repeated using 76.5g. of the latex (37 g. solids). The solid composition (124.2 g.) whenisolated contained 29.8% rubber and 20.4% butadiene. Oncompression-moulding at 200 C. it gave a transparent and very paleyellow plaque. This had full and one-tenth Vicat softening points at 95C. and 85 C. respectively, a breaking stress at -180 C. of 23.3 kg./mm.and a melt viscosity of 21 kp. at 260 C. and a shear rate of 1000/s.

EXAMPLE '9 Resin monomers were copolymerised as described in Example 1in the presence of a rubber latex, not shortstopped, formed of 46% molaracrylonitrile and 54% molar butadiene, and containing 45% solids.

The latex (containing 69.6 g. solids) was used at pH 5.7, withbfphenylmaleimide (2.1 g.), acrylonitrile (9.3 g.), isobutene (2.5 g.),sodium metabisulphite (0.1 g.), potassium persulphate (0.15 g.) andwater (46 emf).

The polymerisation was conducted for 4 hours at 30 C.

The resultant product (containing 83% rubber) was then blended as alatex with a resin latex (formed as above in the absence of rubber) togive a final composition containing 25% rubber. This had full andone-tenth Vicat softening points of 104 C. and 78 C. respectively, abreaking stress at 180 C. of 19.3 kg./mm. a yielding stress at +20 C. of3.8 kg./mm. and a melt viscosity of 10 kp: at 260 C. and a shear rate of1000/s. The melt viscosity remained unchanged over 5 minutes at 260 C.

When the polymerisation was conducted at 35 C., the blended productcontaining 25 rubber otherwise being prepared as described above, thematerial produced had full and one-tenth Vicat softening points of 110C. and 92 C. respectively, a breaking stress at 180 C. of 19.8 kg./mm. ayielding stress at +20 C. of 3.75 kg./ mm and a melt viscosity of 11 kp.at 260 C. and a shear rate of 1000/s. The melt viscosity remainedunchanged over 5 minutes at 260 C. The superstrate/resin ratio is 0.073.

EXAMPLE A rubber graft for blending with a separately prepared resin wasmade by copolymerising acrylonitrile 75% molar), l\ T-phenylmaleimide(5% molar) and isobutene (20% molar) in the presence of a rubber latexnot short-stopped formed of 30% molar acrylonitrile and 70% molarbutadiene and containing 47.5% solids.

The latex (147.5 g.) was adjusted to pH 5.7 and placed with water (680cm. ammonium persulphate (1.40 g.) and sodium metabisulphite (1.08 g.)in a one-litre shaking autoclave, which was then thrice pressurised to 7kg./ cm. with nitrogen and vented. E-phenylmaleimide (10.1 g.) andacrylonitrile (6.15 cmfi) were added, and the autoclave was again thricepressurised to 7 kg./cm. with nitrogen and vented. Finally isobutene(21.9 cm?) was added and the autoclave was shaken at 30 C. for 18 hoursunder nitrogen at about 4 kg./cm. The product was a white latexcontaining 13.5% solids of which about 58% was rubber.

This product was blended with a latex of a homogeneously copolymerizedcopolymer of acrylonitrile (78% molar) and styrene (22% molar) and theblends were coagulated to give strong tough compositions. Theirproperties are tabulated below.

8 EXAMPLE 11 The process described in Example 10 was repeated, exceptthat methyl acrylate (22.7 cm. 20% molar) was used instead of isobuteneand was added to the autoclave with the other monomers. The product wasa latex containing 16.3% solids of which about 47% was rubber. Theisolated graft had full and one-tenth Vicat softening points of C. and78 C. respectively and a yielding stress of 2.4 kg./cm.

The product was blended as a latex with a latex of anacrylonitrile/styrene copolymer as in Example 10 and the blendcoagulated to give a strong tough composition containing 25% rubberhaving full and one-tenth Vicat softening points of 104 C. and 93 C.respectively, a yielding stress of 5.7 k g./mm. and a toughness in thenotched specimen impact test of 2.6 J /cm.. The superstrate/resin ratiowas 0.60.

EXAMPLE 12 Rubber grafts were prepared by the process described inExample 10, using the quantities of rubber and monomers tabulated below.

Starting materials:

Rubber 240 166 180 339 106 Acrylonitrile (g.) 72. 3 72. 3 147. 9 224 224224 N-phenylmaleimide (g.) 15. 7 15. 7 30. 3 45. 4 45. 4 45. 4 Isobutene(g.) 20.4 20.4 42.3 63.5 63.5 63.5 2,400 1,700 2,040 2,500 2,500 2,500.80 1.80 4.0 6.0 6.0 6.0 KzSgOi (g.) 2. 16 2. 16 4. 4 6. 6 6. 6 6. 6Properties of the isolated grafts:

Percent rubber 91 74 66 53 35 29 Breaking stress, kgJmmJ. 0. 3 0. 5 1. 6Yielding stress, lrgJrnm. 2. 4 4. 1 5.0

These grafts as latices were blended with the latex of a resin made by aprocess generally similar to that of Example 10 (but omitting therubber) from acrylonitrile (1750 cm. E-phenylmaleimide (304.5 g.),isobutene (655 cm. sodium metabisulphite 10.37 g.), ammonium persulphate(12.5 g.), sodium dodecyl sulphate (12.25 g.) and octanethiol (5.6 cm)This resin when isolated had a reduced viscosity of 1.0 at 0.5% indimethylformamide at 25 C. The amount of the resin added to each of thegrafts was such that all the final blends contained 20% by weight ofrubber. The products were isolated using 0.75% aqueous calcium chloride,washed and dried. Their properties are tabulated below.

Rubber in graft" by weight,

percent 53 35 Outstanding toughness is shown by the blend made with thegraf containing 53% of rubber.

EXAMPLE 13 A rubber graft for blending with a separately prepared resinwas made by copolymerising acrylonitrile (80% molar) and methyl acrylate(20% molar) in the presence of a rubber latex not short-stopped formedfrom 30% molar acrylonitrile and 70% molar butadiene and containing47.5% solids.

The latex (126.4 g.) was adjusted to pH 5.7 and placed with water (600cmfi), ammonium persulphate (1.20 g.) and sodium metabisulphite (0.99g.) in a one-litre shaking autoclave, which was then thrice pressurizedto 7 kg./ cm. with nitrogen and vented. Acrylonitrile (53.0 cm.) andmethyl acrylate (18.1 cm. were added, and the autoclave was again thricepressurised to 7 kg./cm. with nitrogen and vented. The autoclave wasshaken at 30 C. for 16 hours under nitrogen at about 1.6 kg./cm. Theproduct contained 61% of rubber.

A sample of the graft" latex was coagulated using 0.75 aqueous calciumchloride to give a polymer which was washed twice with water and twicewith methanol ,9 and dried and then gave transparent yellow mouldings at200 C.: full Vicat softening point 6 C.; toughness 1.63 J/cm.

The graf latex was blended with the latex of a resin made by a processgenerally similar to that of Example 11 (but omitting the rubber) fromacrylonitrile (75% molar), E-phenylmaleimide (5% molar) and methylacrylate (20% molar). The amount of the resin latex added was such thatthe resulting blend contained of rubber. The superstrate/resin ratio was0.07. The product was isolated using 0.75% aqueous calcium chloride andwashed and dried. It gave transparent yellow mouldings at 200 C.: fullVicat softening point 94 C.; yielding stress 8.3 kg./mm. toughness 2.10J/cm.

EXAMPLE 14 A rubber graft for blending with a separately prepared resinwas made by copolymerising acrylonitrile (80% molar) and isobutene (20%molar) in the presence of a rubber latex not short-stopped formed from30% molar acrylonitrile and 70% molar butadiene and containing 47.5%solids.

The latex (105.0 g.) was adjusted to pH 5.7 and placed with water (600cmfi), ammonium oersulphate (1.10 g.), sodium metabisulphite (0.91 g.)and acrylonitrile (53.0 cm. in a one-litre shaking autoclave, which wasthen thrice pressurised to 7 kg./crn. with nitrogen and vented.Isobutene (18.7 cm?) was then added and the pressure raised to about 5.6kg./cm. The autoclave was shaken at 30 C. for 17 hours under nitrogen atabout 6 kg./cm. The product contained 64% of rubber.

A sample of the graft isolated as in Example 13 gave transparent ambermouldings at 200 C.

The graf latex was blended with the latex of anacrylonitrile/-phenylmaleimide/methyl acrylate resin as described inExample 13 to give a blend containing 10% of rubber. Thesuperstrate/resin ratio was 0.07. The product was isolated using 0.75%aqueous calcium chloride and washed and dried. It gave transparentyellow mouldings at 200 C.: full Vicat softening point 95 C.; yieldingstress 7.7 kg./mm. toughness 2.28 J/cmfi.

EXAMPLE 15 A rubber graft for blending with a separately prepared resinwas made by copolymerising acrylonitrile (75% molar),lfl-phenylmaleimide (5% molar) and methyl acrylate molar) in thepresence of a polybutadiene latex containing 39.5% solids.

The latex (177.2 g.) was placed with water (680 cm?) and ammoniumpersulphate (1.40 g.) in a one-litre shaking autoclave which was thenthrice pressurised to 7 kg./cm. with nitrogen and vented. Acrylonitrile(61.5 cm. li-phenylmaleimide (10.1 g.) and methyl acrylate (22.7 cm?)were added and the autoclave was again thrice pressurised to 7 kg./cm.with nitrogen and vented. The autoclave was shaken at 60 C. for 17 hoursunder nitrogen at 1.0 to 1.8 kg./cm. The resulting latex contained 15.7%solids of which 47% was rubber.

A sample of the graft isolated as in Example 13 gave transparent brownmouldings at 200 C.: full and onetenth Vicat softening points 89 C. and78 C. respectively; yielding stress 2.0 kg./cm.

' The graft latex was blended with the latex of anacrylonitrile@l-phenylmaleimide/ methyl acrylate resin as described inExample 13 to give blends containing 10% and 20% of rubber, which wereisolated as before. Their properties are tabulated below.

Percent rubber in blend 10 20 Superstrate/resin ratio- 0. 14 0. 39Yielding stress, kg./mm. 9. 1 7. 3 Toughness, .T/cm. 0. 0. 95

EXAMPLE 16 10 in the polymerisation mixture. The graft latices wereblended with the latex of an acrylonitrile/E-phenylmaleimide/isobuteneresin as described in Example 12 to give products containing 10% and 20%of rubber. The properties of the grafts and blends, isolated as before,are tabulated below.

octanethiol used (0111. 0. 5 0. 96 1. 93 Grafts":

Full Vicat softening point C 93 96 91 Mo Vicat softening oint, C 83 85Yielding stress, kg. mm. 3. 1 3. 1 2. 8 Percent of rubber by weight.--48 48 48 Blends containing 10% of rubber (superstrate/ resin ratio 0.14:

Yielding stress, kgJmm. 10.0 10.0 9. 5 Toughness, .T/crn. 0. 14 0. 07 0.16 Blends containing 20% of rubber (superstrate/ resin ratio 0.38):

Yielding stress, kgJmm. 8.1 8. 0 7. 7 Toughness, J lcm. 0.61 0. 63 0. 67

EXAMPLE 17 A rubber graft was made as described in Example 15 but usingisobutene (21.9 cmfi, 20% molar) instead of methyl acrylate. Theisobutene was added as a separate step after the other monomers andafter the cycle of pressurising with nitrogen and venting, and thepolymerisation was conducted for 16 hours at 60 C. under nitrogen at 4to 8 kg./cm. The solids in the resulting latex contained 55% of rubber.

A sample of the graft isolated as in Example 13 gave transparent ambermouldings: full and one-tenth Vicat softening points 107 C. and 94 C.respectively; yielding stress 2.2 kg./mm.

The graft latex was blended with the latex of an acrylonitrile/l-phenylmaleimide/isobutene resin as de scribed in Example 12 to giveproducts containing 10% and 20% of rubber which were isolated as before.Their properties are tabulated below.

EXAMPLE 18 A polybutadiene latex (186.6 g.; 70 g. solids), water (650cmfi), ammonium persulphate (1.4 g.), and acrylonitrile (79.9 cm. 1.2moles) were added to a one-litre shaking autoclave. Air was removed andreplaced by nitrogen. Isobutene (28.4 cm. 0.3 mole) was added and thereaction mixture was shaken for 2 hours at 20 C. and then for 16 hoursat 80 C. under nitrogen at about 7 kg./cm. The solids in the resultingwhite latex contained 50.7% rubber.

A sample of the latex was coagulated with an equal volume of 0.75aqueous calcium chloride at 70 C. The graft copolymer was washed twicewith water and dried. On moulding at 200 C. it gave transparent amberplaques having full and one-tenth Vicat softening points of 92 C. and 77C. respectively and a yielding stress of 2.5 kg./mm. v

The graft latex was blended with a latex of a homogeneouslycopolymerised copolymer of acrylonitrile (78% molar) and styrene (22%molar) to give a blend containing 20% of rubber. The superstrate/resinratio was 0.31. The blended latex was coagulated with 1.5 volumes of0.75% aqueous calcium chloride at 70 C. and the product was washed'twicewith water-and dried. It gave translucent compression-mouldings havingfull and one-tenth Vicat softening points of 104 C. and 92 C.respectively, a yielding stress of 6.4 kg./mm. and a toughness in thenotched specimen impact test of 3.77 I/cmfi. A similarly prepared blendcontaining 15% of rubber (superstrate/ resin ratio 0.20) had a yieldingstress of 7.1 kg./mm. and a toughness of 2.70 I/cm.

The acrylonitrile/styrene copolymer used to make the blend had, whenisolated, a reduced viscosity of 0.88 at 0.5% in dimethylformamide at 25C. and an impact strength of 4.5 J/cm. in an unnotched specimen test.This test was carried out on a specimen 0.9 cm. wide and 0.3 cm. thick,resting horizontally (with the narrow face uppermost) against twosupports 3.8 cm. apart. The specimen was struck centrally on the widerface by a horizontally moving pendulum falling from 30 cm., with morethan sufficient energy to break the specimen. From the residual energyof the pendulum, the energy required to break the specimen wascalculated and then divided by the effective volume (34; x 3.8 x 0.9 x0.3 cm. The resulting value (expressed in joules/cm?) represented theenergy required to cause cracks to form in the material.

EXAMPLE 19 A graft" was prepared as described in Example 18, except thereaction mixture was shaken throughout at 60 C. for 16.5 hours. Theresulting white latex contained 15.2% solids of which 50.7% was rubber.The isolated graft had full and one-tenth Vicat softening points of 93C. and 79 C. respectively and a yielding stress of 2.7 kg./mm. Latexblending with an acrylonitrile/styrene copolymer latex as before gave ablend containing 10% of rubber (superstrate/resin ratio 0.12) having ayielding stress of 7.8 kg./mm. and a toughness of 1.00 J/cm. Theisolated acrylonitrile/styrene copolymer used for this had a reducedviscosity of 0.77 at 0.5% in dimethylformamide at 25 C. and an unnotchedimpact strength of 5.9 I/cm. A blend containing 20% of rubber(superstrate/resin ratio 0.31) made with the resin as used in Example 18had a yielding stress of 6.4 kg./mm. and a toughness of 2.86 J/cmfi.

EXAMPLE 20 A graf was prepared as described in Example 19; it contained50.6% rubber and had full and one-tenth Vicat softening points of 104 C.and 80 C. respectively and a yielding stress of 2.8 kg./mm. This graftwas latex-blended with a series of homogeneously copolymerisedacrylonitrile/ styrene (molar ratio 78:22 latices, the copolymers havingdifferent reduced viscosities (at 0.5% in dimethylformamide at 25 C., togive blends containing 20% of rubber (superstrate/resin ratio 0.32. Theresults are tabulated below.

Graft copolymers were made as described in Example 18, except that thepolymerisation mixture was shaken initially at 20 C. for 2 hours andthen at 80 C. for 4 hours. The table below shows the properties of thegrafts and of the blends containing 20% of rubber made by latex-blendingwith the homogeneously copolymerised acrylonitrile/ styrene latex asused in Example 18; the effect of including octanethiol as a chaintransfer agent in the polymerisation mixtures is also shown.

Octanethiol, cm. 0. 48 0. 95 1. 92 Graft latex, percent:

Solids content.-- 15. 3 15. 2 15. 6 15. 9 50. 48. 9 48. 0

Superstrate/resin ratio 0. 34 0. 33 0.36 0. 37 Full Vicat C 106 105 105105 M0 Vicat, 0-- 97 87 81 94 Yielding stress 6. 9 6. 8 6. 6. 4Toughness--. 1. 96 1. 89 2. 08 2. 07

. I2 EXAMPLE 22 A polybutadiene latex (189.8 g.; 70 g. solids, water(640 cm. ammonium persulphate (1.4 g.), acrylonitrile (79.9 cm. 1.2mole) and ethyl vinyl ether (28.8 cmf"; 0.3 mole were added to aone-litre shaking autoclave. Air was removed and replaced by nitrogenand the mixture was polymerised for 16 hours at 60 C. under nitrogen at7 kg./cm. The resulting white latex contained 16.1% solids of which47.4% was rubber. A sample of the graf copolymer isolated with 0.75%aqueous calcium chloride as before gave transparent amber mouldingshaving full and one-tenth Vicat softening points of 71 C. and 59 C.respectively and a yielding stress of 2.8 k.g./mm. The graf latex wasblended with the homogeneously copolymerised acrylonitrile/styrene latexas used in Example 18 to give a blend containing 20% rubber(superstrate/ resin ratio 0.38). When isolated, it gave translucentcompression-mouldings having full and one-tenth Vicat softening pointsof 104 C. and 94 C. respectively, a yielding stress of 6.4 kg/mm. and atoughness of 1.84 J/cmf".

EXAMPLE 23 A polybutadiene latex (184 g.; 70 g. solids), water (650 cm.ammonium persulphate (1.4 g.), acrylonitrile (79.9 cm. 1.2 mole) andmethyl acrylate (27.1 cm.*; 0.3 mole) were polymerised under nitrogen ina one-litre shaking autoclave for 16 hours at C. The resulting graftlatex contained 16.6% solids of which 45.7% was rubber. This waslatex-blended with a homogeneously copolymerised acrylonitrile/ styrenelatex (molar ratio 78 :22, reduced viscosity 0.86 at 0.5 indimethylformamide at 25 C.) to give a tough strong blend containing 20%of rubber and having superstrate/resin ratio of 0.42.

EXAMPLE 24 A polybutadiene latex (175.5 g.; 70 g. solids), water (655cmfi), ammonium persulphate (1.4 g.), acrylonitrile (66.5 g.; 1.0 mole)and isobutene (39.9 cm. 0.43 mole; added separately as before) werepolymerised under nitrogen in a one-litre shaking autoclave for 4 hoursat 20 C. and then for 12 hours at 80 C. The resulting graft latexcontained 14.4% solids of which 53.7% was rubber. The isolated graft hada yielding stress of 1.8 kg./mm. The graft was latex-blended as beforewith the acrylonitrile/styrene copolymer as used in Example 18 to give ablend containing 20% of rubber (superstrate/ resin ratio 0.27) andhaving a yielding stress of 6.3 kg./ mm. and a toughness of 3.05 J cm.

We claim:

1. A thermoplastic blend of (A) a graft copolymer comprising:

'(i) a substrate of a diene rubber containing 40% to molar of at leastone conjugated 1,3- diene monomer and from 0 to 60% molar of at leastone ethylenically unsaturated monomer copolymerizable therewith usingfree radical catalysts and (ii) a superstrate, which consistsessentially of from 60% to 84% molar of acrylonitrile units, from 0% to20% molar units of at least one E-aryl maleimide and, from 5% to 35%molar of units of at least one alkene containing 2 to 18 carbon atomsand (B) a separately prepared copolymerized resin consisting essentiallyof 60% to 84% molar of units from acrylonitrile, 40% to 16% molar unitsfrom at least one ethylenically unsaturated comonomer which iscopolymerizable with acrylonitrile selected from alkenes, dienes, estersof acrylic and methacrylic acids, vinyl esters, vinyl ethers, esters offumaric acid, unsaturated nitriles, vinyl chloride, vinylidene chlorideand conjugated aromatic olefins, and 0% to 20% molar of units of atleast one E-aryl maleimide, the blend containing from 1% to 50% by 13weight of rubber, the ratio of the superstrate to the separatelyprepared resin in the blend being less than 1.6.

2. A blend of a graft copolymer according to claim 1 wherein theseparately prepared resin contains 60% to 84% molar of units fromacrylonitrile, 40% to 16% molar of units from at least one ethylenicallyunsaturated comonomer selected from alkenes, dienes, esters of acrylicand methacrylic acids, vinyl esters, vinyl ethers, esters of fumaricacid, unsaturated nitriles, vinyl chloride and vinylidene chloride, andto 20% molar of units from at least one E-aryl maleimide, the blendcontaining from 1% to 50% by weight of rubber, the ratio of superstrateto the separately prepared resin in the blend being less than 1.6.

3. A thermoplastic blend of (A) a graft copolymer comprising:

(i) a substrate of a diene rubber containing 40% to 100% molar of atleast one conjugated 1,3- diene monomer and from 0 to 60% molar of atleast one ethylenically unsaturated monomer copolymerisable therewithusing free radical catalysts and (ii) a superstrate, which consistsessentially of from 60% to 84% molar of acrylonitrile units, from 0% to20% molar units of at least one E-aryl maleimide, and from to 35 molarof units of at least one alkene containing 2 to 18 carbon atoms, and (B)a separately prepared homogeneously copolymerised resin consistingessentially of 60% to 84% molar of units from acrylonitrile, 40% to 16%molar of units from at least one conjugated aromatic olefin, and 0% to20% molar of units from at least one E-aryl maleimide, the blendcontaining from 1% to 50% by weight of rubber.

4. A thermoplastic polymer blend consisting essentially of 1 :(A) ahomogeneously copolymerised resin consisting essentially of 60% to 84%molar of acrylonitrile units and 16% to 40% molar of styrene units, and

(B) a graft copolymer comprising:

(i) a substrate of a diene rubber containing 40% to 100% molar of atleast one conjugated 1,3- diene monomer and from 0% to 60% molar of atleast one ethylenically unsaturated monomer copolymerisable therewithusing free radical catalysts and (ii) a superstrate, which consistsessentially of from 60% to 84% molar of acrylonitrile units, from 0% to20% molar of units of at least one lX-aryl maleimide, and from 5% to 35molar of units of at least one alkene containing 2 to 18 carbon atoms,said blend containing 1% to 50% by weight of rubber.

5. A thermoplastic blend of (A) a graft copolymer comprising:

(i) a substrate of a diene rubber containing 40% to 100% molar of atleast one conjugated 1,3- diene monomer and from 0 to 60% molar of atleast one ethylenically unsaturated monomer copolymerisable therewithusing free radical catalysts and (ii) a superstrate, which consistsessentially ofv from 60% to 84% molar of acrylonitrile units,

from 0% to 20% molar units of at least one E- aryl maleimide, and from5% to 35% molar of units of at least one alkene containing 2 to 18carbon atoms and (B) a separately prepared copolymerised resinconsisting essentially of 60% to 84% molar of units from acrylonitrile,40% to 16% molar units from at least one ethylenically unsaturatedcomouomer selected from alkenes, dienes, esters of acrylic andmethacrylic acids, vinyl esters, vinyl ethers, esters of fumaric acid,unsaturated nitriles, vinyl chloride and vinylidene chloride, and 0% to1% molar units of at least one E-aryl maleimide, the blend containingfrom 1% to 50% by weight of rubber, the ratio of superstrate to theseparately prepared resin in the blend being less than 1.6. 6. Athermoplastic 'blend of (A) a graft copolymer comprising:

(i) a substrate of a diene rubber containing 40% to 100% molar of atleast one conjugated 1,3- diene monomer and from 0 to 60% molar of atleast one ethylenically unsaturated monomer copolymerizable therewithusing free radical catalysts and (ii) a superstrate, which consistsessentially of from 45% to molar of acrylonitrile units, from 0% to 20%molar units of at least one garyl maleimide and, from 5% to 35% molarunits of at least one alkene containing 2 to 18 carbon atoms and (B) aseparately prepared copolymerized resin consisting essentially of 45% to90% molar of units from acrylonitrile, 40% to 16% molar units from atleast one ethylenically unsaturated comonomer selected from alkenes,dienes, esters of acrylic and methacrylic acids, vinyl esters, vinylethers, esters of fumaric acid, unsaturated nitriles, vinyl chloride,vinylidene chloride and conjugated aromatic olefins, and 0% to 20% molarunits of at least one Q- aryl maleimide, the blend containing from 1% to50% by weight of rubber, the ratio of the superstrate to the separatelyprepared resin in the blend being less than 1.6.

References Cited UNITED STATES PATENTS 2,802,809 8/ 1957 Hayes 260-8763,153,014 10/1964 Fletcher et al 260879 3,265,708 8/1966 Stiteler 2608793,322,852 5/ 1967 Trementozzi et a1. 260879 3,352,832 11/1967 Barr260780 3,354,108 11/1967 Paradis et al 260-876 3,488,405 1/ 1970Trementozzi et al. 260876 MURRAY TILLMAN, Primary Examiner J. ZIEGLER,Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.

Dated June 11, 197 i Inventor(s) Carl Frager MATHEWS et a1 7 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent. are hereby corrected as shown below:

In the heading, please add the following information:

Assignee: Imperial Chemical Industries Limited,

London, England Claims priority, application Great Britain, April 9,

1965, 15191/65, and application Great Britain, January 12, 1966, l423/66 Signed and sealed this 1st day of April 1975.

'r w) 1 .-4 A. .-.ttest':

C. 32111311 1112 DAY")? RUTZT C. TEE-5C Con'nissioner of PatientsAttesting Off. and Trademarks

